Exemplary embodiments of the invention relate to a fuel cell stack.
U.S. patent document US 2003/0104260 A1 describes a fuel cell system having a housing surrounding at least one first fuel cell stack and a second fuel cell stack situated peripherally with respect to the first fuel cell stack, and which presses the first and second fuel cell stacks together. To this end, the fuel cell system includes tightening straps extending completely around the housing. In addition, the housing may have a cover element that is sealed with respect to the housing.
Furthermore, US 2003/0104260 A1 describes a housing for accommodating and retaining a fuel cell stack during the manufacture of a fuel cell device composed of a plurality of fuel cell stacks, the fuel cell stacks including an end element, a flexible side wall, and a connecting element, and being held together by tightening straps. In addition, methods for manufacturing the fuel cell device are described, comprising stacking the fuel cells in the container, compressing the fuel cells, and engaging the connecting element to retain the fuel cell stack in the stacked configuration, and/or to at least partially compress the fuel cell stack.
Exemplary embodiment of the invention are directed to a fuel cell stack that is improved over the prior art.
A fuel cell stack is formed from a plurality of stacked fuel cell units and at least one stack end element. The stacked fuel cell units and the stack end element are clampable by means of at least one clamping device, and the clamped fuel cell units are surrounded by a housing. According to the invention, a circumferential seal, in particular a lip seal, which has recesses for accommodating the clamping device is situated between the housing and the at least one stack end element, the clamping device being electrically insulated at least in the area of the recesses.
The seal, which is designed as a lip seal, for example, and the electrically insulated clamping device advantageously cooperate in a sealing manner, and thus prevent penetration of moisture into the area between the fuel cell stack and the housing. The combination of the clamping device for clamping the fuel cell stack and the seal of the stack end element with respect to the housing also allows simple and cost-effective production of a sealing system for the fuel cell stack, and saves installation space.
For electrically insulating the clamping device, insulation is formed, preferably molded, onto the clamping device by means of an injection molding process, for example. The insulation is particularly preferably molded onto the clamping device in the area of the housing, thus improving electrical insulation of adjacent fuel cell units.
For positive-fit accommodation of the clamping device, the shape and/or the dimensions of the recesses correspond(s) to the shape and/or the external dimensions of the insulation molded onto the clamping device, resulting in simple installation of the fuel cell stack and ensuring the sealing effect during operation of the fuel cell stack.
The insulation of the clamping device in the area of the recesses is preferably designed in such a way that a positive-fit and/or force-fit connection is established between the insulation of the clamping device and the seal of the stack end element, which is designed in particular as a lip seal, and pretensioning is thus particularly preferably produced that brings about a sealing effect with respect to the lip seal, and thus, the housing. To increase the pretensioning, the insulation of the clamping device has a thickened area in places, in particular in the area of the recesses.
To optimize the sealing effect of the insulation of the clamping device and of the seal, the insulation and the seal are made of a rubber, a foam, polyvinyl chloride, thermoplastic polyurethane, and/or a thermoplastic polymer. These electrically insulating materials are characterized by high chemical resistance, high heat resistance, and good corrosion properties.
The clamping device includes at least one strip- or band-shaped tightening strap encircling the stacked fuel cell units and the stack end element. This type of tightening strap has low weight and low space requirements, and is also easy and cost-effective to manufacture and install. The clamping device particularly preferably includes multiple tightening straps, thus advantageously optimizing compression of the fuel cell stack and increasing a sealing effect between the fuel cell stack and the housing.
In one particularly preferred embodiment of the invention, the tightening strap is made of glass fiber or stainless steel. Materials made of glass fiber and stainless steel are resistant to corrosion and chemical attack, and in particular glass fiber materials also have a high modulus of elasticity.
The stack end element of the fuel cell stack particularly preferably forms a cover of the housing, which in particular is designed as a housing that is open on one side. The requirements for installation space and components are thus optimized. The stack end element therefore meets multiple functions, in which it is used as an end-face delimitation of the stacked fuel cell units and also as a cover element of the fuel cell stack.
Alternatively or additionally, the housing is designed as a housing which is open on two sides, and the fuel cell stack includes two stack end elements, one of the stack end elements forming the cover, and the other of the stack end elements forming the base, of the fuel cell stack.
Mutually corresponding parts are provided with the same reference numerals in all the figures.